Mode I toughening of bio-based epoxy adhesive through 3D-printed biomimetic reinforcements
Topic(s) : Special Sessions
Co-authors :
Ran TAO (NETHERLANDS), Zhiyuan XU (NETHERLANDS), Sofia TEIXEIRA DE FREITAS (NETHERLANDS)Abstract :
Climate change is a major global issue that impacts both the environment and human society, requiring an immediate huge effort in enhancing sustainability in the aerospace industry. Using adhesive bonding of composites is a rising state-of-the-art technique for more efficient, sustainable, and lightweight aircrafts. Besides, conventional adhesive materials are petroleum-based epoxy resins, causing growing environmental, healthy, and economic concerns due to the harmful industrial processes and finite petrochemical resources. This evolution is essential for positioning bio-based adhesive materials as attracting options for integration into load-bearing structures. To enhance sustainability and concurrently uphold joint safety and reliability, there is a compelling need to improve the mechanical properties of adhesively-bonded composite joints using the bio-based epoxy adhesive.
A promising pathway to improve fracture resistance is to introduce crack arrest features and achieve progressive failure within adhesive joints, mainly relying on extrinsic bridging phenomena. The adhesive layer can be directly utilized to bridge the separating CFRP parts, triggered by the patterning of distinct surface treatments [1]. Moreover, the polymer carrier within the adhesive film, originally aiming for maintaining the bondline thickness, is proven to largely enhance the energy release rate (ERR) and successfully arrest the crack propagation [2]. In this work, we further developed the extrinsic toughening mechanism under the mode I fracture loading of adhesive joints, focusing on the biomimetic design of polymer structures integrated within a bio-based epoxy adhesive.
By mimicking the molecular structure of spider silk, which is one of the toughest materials in nature, we manufactured polymer structures containing sacrificial bonds and hidden lengths through the 3D-priting. Such 3D-printed bio-mimic reinforcements, or overlapping curls (OCs), were integrated within a bio-based epoxy adhesive. The adhesive layer of double cantilever beams (DCB) was architected to trigger the extrinsic bridging, promote progressive failure, and improve the mode I ERR. Results proved that the proposed 3D-printed OC structures are promising in toughening the bio-based DCB adhesive joints. The printing and manufacturing parameters could tune the failure responses of OC, thus altering their ability to arrest crack propagation within the integrated bio-based adhesive layer. It has shown that the sacrificial bond intrinsically hinders the crack propagation, while the hidden length extrinsically bridges the separating DCB arms, paving a novel path towards safer and more sustainable aerospace structures.
A promising pathway to improve fracture resistance is to introduce crack arrest features and achieve progressive failure within adhesive joints, mainly relying on extrinsic bridging phenomena. The adhesive layer can be directly utilized to bridge the separating CFRP parts, triggered by the patterning of distinct surface treatments [1]. Moreover, the polymer carrier within the adhesive film, originally aiming for maintaining the bondline thickness, is proven to largely enhance the energy release rate (ERR) and successfully arrest the crack propagation [2]. In this work, we further developed the extrinsic toughening mechanism under the mode I fracture loading of adhesive joints, focusing on the biomimetic design of polymer structures integrated within a bio-based epoxy adhesive.
By mimicking the molecular structure of spider silk, which is one of the toughest materials in nature, we manufactured polymer structures containing sacrificial bonds and hidden lengths through the 3D-priting. Such 3D-printed bio-mimic reinforcements, or overlapping curls (OCs), were integrated within a bio-based epoxy adhesive. The adhesive layer of double cantilever beams (DCB) was architected to trigger the extrinsic bridging, promote progressive failure, and improve the mode I ERR. Results proved that the proposed 3D-printed OC structures are promising in toughening the bio-based DCB adhesive joints. The printing and manufacturing parameters could tune the failure responses of OC, thus altering their ability to arrest crack propagation within the integrated bio-based adhesive layer. It has shown that the sacrificial bond intrinsically hinders the crack propagation, while the hidden length extrinsically bridges the separating DCB arms, paving a novel path towards safer and more sustainable aerospace structures.